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PubMed2004

Pulp size in molars: underestimation on radiographs.

The aim was to determine whether radiographs provide a clinically useful indication of pulp size in diseased/restored human first molar teeth, and to investigate accessibility of pulp tissue for diagnostic testing using laser Doppler flowmetry (LDF). Extracted teeth of known age were collected. Restorative materials were removed and teeth with evidence of pulp exposures excluded. Fifty-six teeth were radiographed from buccal and mesial aspects, and then their crowns were sectioned axiobuccolingually and photographed. Images were digitally scanned and measurements made of the total pulp area (above a line across the most superior part of the pulpal floor) and the pulp area in the clinical crown (superior to a line between the amelocemental junctions). The pulp width at the cervix and the highest point of the pulp were also recorded. Data were analysed using Pearson correlations. Pulp areas within the clinical crowns were significantly larger than indicated by radiographs, by 23% in the case of the clinically attainable buccal view (P < 0.05). Pulps may be more accessible to flowmeter testing than they appear. Absence of pulp tissues in the crown was recorded in equal numbers of teeth on radiographs and sections, but with agreement for only one tooth. Sixteen per cent of the teeth had no pulp area in the clinical crown when sectioned, but might still be suitable for testing using LDF.

Adult↗

PubMed2006

[Analysis of the movement of long axis and the distribution of principal stress in abutment tooth retained by conical telescope].

OBJECTIVE: To study the movement of long axis and the distribution of principal stress in the abutment teeth in removable partial denture which is retained by use of conical telescope. METHODS: An ideal three dimensional finite element model was constructed by using SCT image reconstruction technique, self-programming and ANSYS software. The static loads were applied. The displacement of the long axis and the distribution of the principal stress in the abutment teeth was analyzed. RESULTS: There is no statistic difference of displacenat and stress distribution among different three-dimensional finite element models. Generally, the abutment teeth move along the long axis itself. Similar stress distribution was observed in each three-dimensional finite element model. The maximal principal compressive stress was observed at the distal cervix of the second premolar. CONCLUSION: The abutment teeth can be well protected by use of conical telescope.

Crowns↗

PubMed1996

Fractures of hydroxyapatite-coated blade implants connected with natural teeth. A histological study using SEM, light microscopy, and an image processing system.

A clinical study was conducted of 59 patients treated with 78 hydroxyapatite (HA)-coated blade implants from August 1986. Five implants in 5 patients were broken at the neck portion, and one implant in one patient was removed from the jaw bone. The histological findings around a broken implant which was removed from the mandible are presented. These sections showed good adaptation of the bone to the implant without a fibrous layer. Histomorphometric evaluation of bone-to-implant contact showed 73.5%. The scanning electron microscopy image of the fractured surface revealed a fatigue fracture. The suspected cause of the fracture was stress concentration at the cervix portion, because of excessive mobility or deleterious change of abutment teeth. Consequently, the osseointegration/biointegration implants should not be connected with natural teeth.

Aged↗

PubMed1990

Early hominid dental pathology: interproximal caries in 1.5 million-year-old Paranthropus robustus from Swartkrans.

Carious lesions on the mesial and distal aspects of a RM1 of a young adult 'robust' australopithecine. Paranthropus robustus, are described. The specimen is from Member 1 sediments of the Swartkrans cave, which are dated to between about 1.8 and 1.5 million years before present. The mesial lesion, located cervically, had progressed further than the two distal lesions, which were situated along the cervix and in the enamel of the interproximal contact facet. This is the third specimen of P. robustus to be discovered with dental caries, but the other two cases were associated with occlusal and buccal enamel hypoplasia. Caries is present in less than about 3.0% of the approx. 116-128 P. robustus specimens at Swartkrans, and this incidence is noticeably lower than in the small Homo erectus sample from the same site. While this difference may simply be a sampling artefact, it may reflect dietary differences between these two synchronic and presumably sympatric early hominid species.

Adult↗

PubMed2003

Accidentally induced periodontitis in primary dentition: longitudinal examinations of periodontal bacteria and clinical conditions.

Periodontitis is very rare in the primary dentition although it can be accidentally induced in young children. The purpose of this study was to describe a case of periodontitis in a 4-year-old child, which was accidentally induced by insertion of small plastic tubes into the dental cervix of the primary incisors during play, and to discuss the clinical, radiographic, and microbiological findings. Removal of the plastic tubes resulted in resolution of the periodontal condition. Prevotella nigrescens and Campylobacter rectus were detected in subgingival plaque samples from the affected teeth at every examination, whereas Porphyromonas gingivalis, Treponema denticola, Prevotella intermedia, and Bacteroides forsythus were never found during the two-year observation period. The clinical and microbiological results suggest that the type of periodontitis caused by such an incidence is not progressive, unlike other periodontal diseases such as prepubertal and juvenile periodontitis.

Accidents↗

PubMed2006

Analysis of the surface characteristics and mineralization status of feline teeth using scanning electron microscopy.

External resorption of teeth by odontoclasts is a common condition of unknown origin affecting domestic cats. Odontoclastic resorptive lesions involve the enamel cementum junction (ECJ, cervix) and root surface, leading to extensive loss of enamel, dentine and cementum. This study was undertaken in order to determine whether features of the surface anatomy and mineralization of feline teeth could explain why odontoclastic resorptive lesions are so prevalent in this species. Backscattered electron scanning electron microscopy was used to study enamel, cementum and dentine in non-resorbed, undemineralized teeth from adult cats. Analysis of the ECJ revealed thin enamel and cementum and exposed dentine at this site. Furthermore, enamel mineralization decreased from the crown tip to the ECJ, and dentine mineralization was lowest at the ECJ and cervical root. Analysis of cementum revealed variations in the organization and composition of fibres between the cervical, mid- and apical root although no significant differences in mineralization of cementum were detected between different regions of the root. Reparative patches associated with resorption of cementum by odontoclasts and repair by cementoblasts were present on the root surface. In conclusion, results suggest that the ECJ and cervical dentine could be at a greater risk of destruction by odontoclasts compared with other regions of the tooth. The relationship of these features to the development and progression of resorption now requires further examination.

Animals↗

PubMed1998

Retrograde sealing of accidental root perforations with dentin-bonded composite resin.

Surgical treatment was performed on 100 iatrogen perforations, of which 94 showed radiolucency of bone adjacent to the perforation and 83 presence of an exposed post. The perforations were in all cases sealed with a resin composite (Retroplast) bonded to adjacent root dentin with a dentin bonding agent (Gluma). Cases were examined after approximately 1 yr (first recall) and, if necessary after 1 1/2 to 11 yr (mean: 4.1 yr) (latest recall). It was observed that the presence or absence of bone on the root between the perforation and cervix at the time of operation had no significant effect on the healing result, and that the radiographic classification "partial" healing with a border of cortical bone or a lamina dura often remained unchanged for many years. At latest recall, the healing result of 65 teeth originally having root perforation elsewhere than at the furcation was: 71% complete, 11% partial, 3% uncertain, and 15% failure. This is significantly different from the healing result of 27 molar teeth originally having perforation at the furcation: 30% complete, 41% partial, 11% uncertain, and 18% failure.

Adult↗

PubMed2006

[Study on root fracture and alveolar bone absorption of doweled lower premolars].

PURPOSE: The aim of this study was to examine root fractures in the doweled lower premolars and their relationship to alveolar bone absorption on the buccal aspect of the abutment teeth. METHODS: Experiment 1. Fractures in the roots of the abutment teeth and absorption of the surrounding alveolar bone was visualized by Multi-image Micro CT (3DX) in nine lower premolar abutment teeth that had lost both their posts and their. Experiment 2. The stresses in the teeth were analyzed using a three-dimensional finite element model, both models with and without alveolar bone absorption, as determined from Experiment 1. The stress distributions of von Mises equivalent stress and the shear stresses in the XZ, YZ and XY direct ions were examined. RESULTS: Experiment 1. The absorption of the alveolar bone was observed on the buccal side, and the fractures in the roots were observed in the lingual to buccal direction. Experiment 2. In the case without alveolar bone absorption, the XY shear stress in the root for mesial or distal loads was concentrated near the cervix with a positive stress value, and close to the end of the post with a negative stress value. In the alveolar bone absorption model, the XY shear stress in the root for mesial or distal loads was concentrated close to the end of the post on the lingual side with a positive stress value and on the buccal side with a negative stress value. CONCLUSION: In the case without alveolar bone absorption, on stress concentration was observed at the end of the post. Otherwise, based on the results of the finite element model analysis, for mesial or distal loads, the root fracture in the abutment teeth would be considered to be caused by absorption of the alveolar bone and the buccal aspect.

Alveolar Bone Loss↗

PubMed2004

Effect of orthodontic forces on root resorption in molars submitted to experimental periodontitis.

The present experimental study addresses the issue of the development and size of root resorption areas in molars of rats submitted to orthodontic forces of 51 or 75 g and the induction of periodontal disease by placing a cotton ligature around the cervix of the first upper molars for 48 hours. Immediately on removal of the ligature or 48 hs later we put an orthodontic device in place. The device comprised two steel bands. The arms of a helicoidal spring that exerted force towards palatine passed through the palatine tubes welded to the bands. The number of odontoclasts and the percentage of root resorption areas were determined histomorphometrically on bucco-palatine sections obtained at the level of the central roots. The data showed an increase in root resorption areas when the orthodontic forces were applied to molars of rats following the induction of periodontitis. The magnitude of the force was proportional to the size of the resorption areas and to the number of odontoclasts. Both these end-points exhibited smaller values when the forces were applied once the inflammatory reaction had subsided. The present study shows that the risk of development of root resorption areas in patients with periodontal disease submitted to orthodontic treatment would be lower if lighter forces were applied and treatment were delayed until the inflammatory signs have subsided.

Animals↗

PubMed1982

The normal human anaerobic microflora.

Anaerobic bacteria are prevalent among the bacterial populations of the human body, particularly on mucous membrane surfaces. The major sites with a rich anaerobic normal microflora are the mouth, the gastrointestinal tract and the female genital tract. The oral cavity harbours more than 300 different bacterial species. The concentrations of bacteria in saliva are 10(8) to 10(9) colony forming units/ml and anaerobic bacteria outnumber aerobic bacteria by 10:1. On the tooth surfaces, the concentrations of bacteria are 10(10) to 10(11) cfu/ml with a predominance of anaerobes. Bacterial concentrations in gingival scrapings are 10(11) to 10(12) cfu/ml with anaerobic bacteria outnumbering aerobic bacteria by 1000:1. In the saliva and on the tongue surface, the predominant anaerobic bacteria are cocci, while in the gingival crevice large concentrations of gram-negative rods are recovered. Microorganisms found in the upper intestinal tract are different from those in the lower intestinal tract. In the stomach and the proximal small bowel, the microorganisms found as normal flora are a reflection of the oral flora. Bacterial concentrations in this region are 10(2)-10(5) cfu/ml intestinal content. In the colon, bacterial concentrations of 10(11)-10(12) cfu/g faeces are found. About 500 different bacterial species are recovered in the lower intestine. The most common anaerobic microorganisms are bifidobacteria, lactobacilli and bacteroides. Recent studies have used quantitative techniques for analyses of the vaginal flora and it has been found that anaerobic bacteria outnumber aerobic bacteria in the vagina by approximately 10:1. The most prevalent bacteria are peptococci, present in counts of 10(7)-10(8) cfu/ml. Lactobacilli, corynebacteria, eubacteria and bacteroides are also isolated.

Anaerobiosis↗

PubMed1993

Resistance to vertical fracture of roots, previously fractured and bonded with glass ionomer cement, composite resin and cyanoacrylate cement.

A recently developed glass ionomer bone cement (Ionos) may be suitable for bonding vertically fractured teeth, but the resulting resistance to repeated fracture of the bonded teeth is unknown. The purpose of this study was to assess in vitro the resistance to repeated fracture of roots which were previously fractured and bonded with Ionos cement and other bonding agents. Thirty-six roots were separated at the cervix and grooved on the coronal surface. Each root was mounted in an Instron machine and a vertical force was exerted until fracture occurred. Both the force required to fracture the root (F) and the root surface area (A) were recorded, and the root halves were bonded with one of the following materials: Ionos bone cement without dentin etching, Permabond 910 cyanoacrylate adhesive, and Gluma bonding system. The bonded roots were maintained in a wet sponge. One week later the roots were re-fractured in the Instron machine, and the forces were recorded (RF). Each one of F, RF, A, and the ratios RF/F and RF/A were compared statistically among the three experimental groups. Overall, RF was at the most 20% of F. Statistically significant differences were obtained only in RF, RF/F, and RF/A (p < 0.0003). Roots bonded with Ionos cement demonstrated significantly lower values than roots bonded with Permabond and Gluma, both of which did not differ significantly. It was concluded that roots bonded with Ionos cement were the least resistant to re-fracture, due to a lesser bonding strength of Ionos bone cement as compared with Permabond and Gluma.

Acid Etching, Dental↗